Disc brakes not stopping?

[amberkalvin]

I've researched and have built a good handful of trucks and have done tons of brake jobs. However, this one has me stumped...

I have something that looks like this kit

And it seems no matter what I can't get enough pressure to stop the truck. I've ruled out vacuum since this truck has a large cam and went ahead and put a $230 vacuum pump as well as a vacuum canister that is supposed to pull at least 18" of vacuum. The engine only pulls 12". I can leave it for 10 or 20 mins and pull a vacuum line off and hear a bunch of pressure release so I don't imagine the booster is bad.

All rubber lines are new, freshly turned rotors, new pads and brand new calipers. Properly bled with a firm pedal. Brand New master cylinder off of a 74 c10 as I thought it might've been bad, plumbed to match my K5 which stops like a champ and a brand new proportioning valve.

My thought is this. With the setup I have now, I am losing leverage by the pivoting portion of the booster bracket. Whereas this kit listed below is straight from the pedal to the booster.


https://www.summitracing.com/parts/c...EaAh3iEALw_wcB

Any help would be greatly appreciated. I have never run across this kind of issue.